BACTERIOLYSIS 39 



soever. All experiments have been uniformly negative in attempt- 

 ing to obtain multiplication of the bacteriophage by contact of 

 the ultramicrobe with bacteria killed by age, by heat, by chloro- 

 form, by thymol, by the essences of cinnamon and mustard, by 

 alcohol, by bichloride of mercury, by phenol, by sulfuric and 

 hydrochloric acids, and by iodine. With such suspensions no 

 action whatever is secured; no lysis and no culture of ultrami- 

 crobes. 



The bacteriophage is an obligatory parasite, multiplying only 

 at the expense of living bacteria. 



An experiment of the following nature is interesting in that 

 it shows that the bacteriophage will attack only normal bacteria. 

 The bacteria are suspended in a medium containing an antiseptic 

 in a quantity so small that the bacteria will only be killed after a 

 time exceeding that required for the lytic process of the bacte- 

 riophage. In such a case the bacteria are not affected by the 

 bacteriophage and the latter fail entirely to 'proliferate. The 

 antiseptic selected was, by intention, one without action on the 

 diastases, sodium fluoride. 



In a one per cent solution of sodium fluoride in bouillon the Shiga 

 bacilli are still cultivable after thirty-six hours, a time more 

 than adequate for the bacteriophage to manifest its lytic activ- 

 ity and to multiply. Furthermore, if transfers in series are made 

 with such a suspension, inoculating the first tube with a drop of 

 the bacteriophage culture; the second, after incubation for twenty- 

 four hours, with a drop of the first; the third with a drop of the 

 second, and so on, it will be found that the bacteriophage disap- 

 pears with the transfer from the second to the third tubes of the 

 series (this can be confirmed by placing a drop of each tube into a 

 suspension of normal bacilli). Controlling this procedure with 

 a second series, using pure bouillon or even sterile water, it will 

 be found that here likewise the bacteriophage will not be present 

 in the third or fourth tube. This is, as will be seen later, simply 

 a result of dilution. The bacteriophagous germ, therefore, can 

 not be cultivated in a suspension containing fluoride, in sterile 

 bouillon, or in pure water. 



Moreover, it has been shown that it is solely because of the 

 medium into which it is introduced that the bacillus is not sub- 



